This invention relates to a semiconductor resistor device, and more particularly to a semiconductor resistor device which can trim resistance with a high precision.
With a digital-analog converter or analog-digital converter, a precise resistance value generally determines the reliability of the converter circuit. Therefore, a resistor of high precision is required for such converter. However, a thin resistor device of the hybrid type proposed to date for this object has the drawbacks that the resistor device has a low moisture proof property and is manufactured by a complicated process. On the other hand, a diffusion type resistor or polycrystalline silicon resistor manufactured during the conventional semiconductor-manufacturing process must be allowed to have variations of at least about 0.4% in resistance value in consideration of deviations occurring in the factors involved in the conventional semiconductor device-manufacturing process. Yet, the above-mentioned type of resistor has the advantage that it can be easily manufactured at low cost. At present, therefore, this type of resistor is still put to practical application by trimming its resistance value. One of the known resistor-trimming processes comprises connecting a plurality of diffusion type resistors in parallel by electrode metals of, for example, aluminum, and cutting the intervening electrode metals by laser beams, thereby raising the resistance of the portion including all the diffusion type resistors to a prescribed level. Another known resistor-trimming process comprises destroying part of a polycrystalline silicon resistor by laser beams. However, the above-mentioned conventional resistor-trimming processes destroy part of an electrode metal or semiconductor device by high output laser beams, presenting difficulties in assuring the reliability of a resistor device as a whole, and further imposing certain limitations on the construction of the resistor device.